XPS: in situ

When doing in situ XPS in solid state electrochemistry one must be aware of the following experimental realities 6,56 62... 

In summary in situ XPS with metal/YSZ catalyst-electrodes has positively confirmed the O backspillover mechanism as the cause of NEMCA and has provided very interesting information about the strongly anionic state of the backspillover oxygen species. On the basis of the energetic indistinguishability of the backspillover Cf on the Pt surface and O2 in the YSZ revealed by XPS, it appears almost certain that Cf is. Nevertheless and in anticipation of... 

Reversible sodium backspillover as the origin of electrochemical promotion when using Na+ conductors, such as P"-A1203, as the solid electrolyte has been confirmed by the in situ XPS work of Lambert and coworkers.56 61... 

The availability of in situ XPS accompanying STM therefore provides both chemical characterisation of the adlayer and the concentrations of adatoms... 

It is frequently asserted that two weaknesses of STM are first that all atomic asperities in images need not necessarily correspond to atom surface positions and second that it is inherently difficult to establish the identity of imaged atoms when two or more surface species are involved. The latter need not, however, be a problem. In a study (for example) of the oxidation of ammonia at Cu(110) the oxygen and nitrogen adatoms form separate individual structures which run in the < 100 > and < 110 > directions, respectively, whereas under ammonia-rich conditions only imide species are formed, running in the < 110 > direction, with in situ XPS confirming their presence and the absence of surface oxygen (Chapter 5). 

What is a possible reason for the small amount of studies carried out using in situ XPS ... 

In general, the mechanistic model established for the ODH of ethylbenzene can be adapted to alkanes (Fig. 15.11(d)). In situ XPS analyses of CNT catalysts during ODH of n-butane show sensitive response of the band located at 531.2 eV, which is assigned to carbonyl oxygen [63]. If oxygen is removed from the atmosphere, the intensity of... 

In each of the studies described so far, XPS was measured under UHV conditions. However, previous studies of oxide catalysts [100] have shown that by using a specially designed high-pressure in situ XPS apparatus, XP spectra can be measured under reaction conditions in the mQUbar pressure range. This technique was appUed to a selection of , 0 /5-alumina catalysts (l-8wt% V) to determine their electronic structure under oxidative and reaction (n-butane) atmospheres... 

Gabasch H, Hayek K, Klotzer B, Unterberger W, Kleimenov E, Teschner D, et al. (2007). Methane oxidation on Pd(lll) in situ XPS identification of active phase. J Phys Chem C, 111,1951... 

Velu, S., Suzuki, K., Vijayaraj, M., Barman, S., and Gopinath, C.S. In situ XPS investigations of Cu 1-x Ni x ZnAl-mixed metal oxide catalysts used in the oxidative steam reforming of bioethanol. Applied Catalysis. B, Environmental, 2005, 55, 287. 

Both types of catalysts have been successfully used for the hydrogenation of acrolein and acetophenone to improve the selectivity to allyl alcohol and phenylethanol, respectively [19]. Finally, it could be possible too, that the interaction of Ag with lanthanum or manganese oxides may result in a modification of the electronic environment of Ag because of the electron donation properties brought about their basicities. Therefore, in-situ XPS measurements are currently performed to assess the oxidation state of the metals in the working catalyts. 

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